Influenza: Clinical Presentation and Complications

Influenca ili gripa akutna je bolest dišnog sustava uzrokovana virusima influence. Virusi influence neprestano se mijenjaju, a antigenske promjene virusa influence A odgovorne su za epidemije koje se pojavljuju svake godine u zimskim mjesecima te za pandemijsko pojavljivanje influence svakih nekoliko desetljeća. Influenca je klinički obilježena ponajprije općim simptomima, povišenom temperaturom i glavoboljom, umorom te bolima u mišićima. Respiratorni simptomi se obično pridružuju nakon dan-dva, poglavito suhi kašalj i grlobolja. Influenca je, u pravilu, teška bolest zbog brojnih komplikacija koje mogu biti uzrokovane samim virusom influence ili sekundarnim bakterijskim infekcijama. Komplikacije su najčešće u dišnom sustavu, osobito upale pluća, ali mogu biti zahvaćeni i drugi organski sustavi. Upala pluća vrlo je česta i teška, a nerijetko i pogibeljna komplikacija influence jer je odgovorna za golemu većinu smrtnih slučajeva. Klinički i patofiziološki razlikuju se dva oblika pneumonija u influenci. To je primarna virusna pneumonija uzrokovana samim virusom influence, a pojavljuje se u početku bolesti i sekundarna bakterijska pneumonija koja se obično pojavljuje u drugom tjednu bolesti. U djece se pneumonija pojavljuje mnogo rjeđe nego u odraslih, a relativno često dijagnosticiraju se laringitis, krup i bronhiolitis, zatim pogoršanje kroničnog bronhitisa i astme te česte bakterijske superinfekcije s upalom uha i sinusa. Zahvaćenost živčanog sustava u tijeku influence češća je u djece nego u odraslih. Neurološke komplikacije influence uključuju konvulzije, encefalopatiju, meningitis i encefalitis, Guillain-Barréov sindrom, transverzalni mijelitis te Reyeov sindrom. Relativno često registrira se oštećenje jetre, a rjeđe miozitis, miokarditis i perikarditis. U nekih se bolesnika razvija rabdomioliza s akutnim zatajenjem bubrega. Bolest koju uzrokuje pandemijski virus A(H1N1) klinički se bitno ne razlikuje od sezonske influence. Najvažnija je razlika češće obolijevanje s većim brojem komplikacija i smrtnih ishoda u mlađih od 55 godina, a u sezonskoj influenci većina se komplikacija i smrti registrira u starijih od 65 godina. Najčešća je komplikacija pandemijske influence primarna virusna pneumonija, nerijetko s razvojem akutnoga respiratornog distres sindroma (ARDS), a sekundarne bakterijske infekcije pojavljuju se rijetko.Influenza or flu is an acute respiratory disease caused by influenza viruses. Influenza viruses are continuously changing, and antigen changes of influenza A virus are responsible for epidemics occurring each winter and for pandemics occurring every several decades. The clinical features of influenza primarily include general symptoms, i.e. high temperature and headache, muscle pain and fatigue. Respiratory symptoms, primarily dry cough and sore throat, usually occur after a day or two. Generally, influenza is a serious disease due to a number of complications that may be caused by either influenza virus itself or secondary bacterial infections. The most frequent complications are respiratory complications, especially pneumonias, but other organ systems may be also affected. Pneumonia is a very common, severe and often fatal complication of influenza because it is responsible for the majority of fatal outcomes. Clinically and pathophysiologically, there are two forms of pneumonias in influenza. These are primary viral pneumonia caused by influenza virus, which occurs at the onset of the disease, and secondary bacterial pneumonia, which usually occurs during the second week of the disease. In children, pneumonia occurs much more rarely than in adults. Laryngitis, croup and bronchiolitis have been observed relatively frequently, as well as exacerbation of chronic bronchitis and asthma. Bacterial superinfections with otitis and sinusitis have been also frequently observed. Nervous system is more frequently affected in children than in adults. Neurological complications of influenza include convulsions, encephalopathy, meningitis and encephalitis, Guillain-Barré syndrome, transverse myelitis and Reye’s syndrome. Hepatic impairment has been observed relatively frequently, while myositis, myocarditis and pericarditis have been observed rarely. Rhabdomyolysis with acute renal failure has been recorded in some patients. The clinical features of the disease caused by pandemic virus A (H1N1) are not significantly different from those of seasonal influenza. The most important difference is a higher morbidity and a greater number of complications and fatal outcomes in patients below the age of 55, while in seasonal influenza, the majority of complications and fatal outcomes have been recorded in patients above the age of 65 years. The most frequent complication of pandemic influenza is primary viral pneumonia, often accompanied by acute respiratory distress syndrome (ARDS), while secondary bacterial infections occur rarely